Question

I have a database with patients, doctors, cabinets and visits.

Patients (id_pac, FirstName, LastName)

Doctors (id_med, FirstName, LastName, Speciality)

Cabinets (id_cab, Name)

Vizits (id_viz, Date_viz, Medic_id,Patient_id, Cabinet_id)

One doctor can make visits on different patients, on different cabinets, on different dates.

I need to find out (with a subquery or with a join ? , but NOT with intermediary tables or views), in one report :

1. one column with the doctor’s complete name : CONCAT(FirstName,’ ‘,LastName) (DISTINCT),
2. one column with the cabinet name in which the doctor was having the biggest number of visits
   and
   3.one column with the number of visits for this cabinet.

I have tried to figure out how can i get this information, but all what I can have is
the list of doctors with every cabinets in which he was having visits, with the total number of visits / cabinet :((

Answer 1

SELECT CONCAT(d.FirstName,' ',d.LastName) AS CompleteName
     , c.Name                             AS CabinetName  
     , dv.MaxVisits                       AS MaxVisits
FROM Doctors AS d
  LEFT JOIN
    ( SELECT Medic_id
           , MAX(NumVisits) AS MaxVisits
      FROM
        ( SELECT Medic_id
               , Cabinet_id
               , COUNT(*) AS NumVisits
          FROM Vizits AS v
          GROUP BY Medic_id
                 , Cabinet_id
        ) AS grp
      GROUP BY Medic_id
    ) AS dv
    ON dv.Medic_id = d.id_med
  LEFT JOIN
    ( SELECT Medic_id
           , Cabinet_id
           , COUNT(*) AS NumVisits
      FROM Vizits AS v
      GROUP BY Medic_id
             , Cabinet_id
    ) AS mcv
    ON  mcv.Medic_id = dv.Medic_id
    AND mcv.NumVisits = dv.MaxVisits
  LEFT JOIN Cabinets AS c
      ON c.id_cab = mcv.Cabinet_id